Exhaust manifolds for internal combustion engines may be exposed to high thermal loads. Exhaust manifolds that are integrated into cylinder heads (IEM cylinder heads) may experience particularly high thermal loading due to the heat transfer characteristics of the integrated design. For example, IEM cylinder heads may channel exhaust to a single exhaust outlet port, which experiences a high thermal load during operation of the vehicle.
Thermal loading of an integrated exhaust manifold and neighboring components can be reduced by incorporating coolant jackets into the cylinder head. The coolant jackets with a coolant core formed therein can reduce the thermal stresses on the cylinder head caused by heat generated during engine operation. For example, a cylinder head having an integrated exhaust manifold is disclosed in U.S. Pat. No. 7,367,294. Upper and lower coolant jackets encompass a major portion of the cylinder head to remove heat from the cylinder head via heat exchange with a circulated liquid coolant.
However, the inventors herein have recognized issues with the above described approach. In one example, exhaust gases may be insufficiently cooled. Under such conditions, the temperature of cylinder head will increase in a region of the cylinder head proximal to the exhaust passages, particularly in a region proximal to the single exhaust port. As a result, the cylinder head and/or other cylinder components may be thermally degraded too quickly. Further, downstream engine or vehicle components, such as a turbocharger and/or an emission control system, may be thermally degraded. In another example, sharing a single exhaust passage may increase flow or pressure pulsation communication between cylinders. During overlapping pulses of cylinders, one or more cylinders may receive high pressure exhaust blowdown from another cylinder, and thus engine efficiency may be reduced.
As such, various example systems and approaches to address the above issues are described herein. In one example, an engine cooling system comprises a cylinder head including an integrated exhaust manifold that directs exhaust gases to an exhaust port, a coolant passage surrounding the exhaust manifold, and a cluster of exhaust passages for directing exhaust gases to the exhaust port, the cluster of exhaust passages including at least one drill hole disposed within a material linking exhaust passages in the cluster of exhaust passages, the at least one drill hole fluidically coupled to the coolant passage. Further, the cluster of exhaust passages may comprise a first exhaust runner coupled to a first cylinder, a second merged exhaust runner coupled to a second cylinder and a third cylinder, and a third exhaust runner coupled to a fourth cylinder. Furthermore, the cylinder head may include a temperature sensor disposed in a top wall of the cylinder head above the exhaust port.
In this way, the cooling system may at least partially provide overheat protection to an engine, while reducing communication between cylinders. For example, coolant flow may be provided between the exhaust runners. As a result, a greater cooling surface area may be provided to the exhaust gas face for heat exchange with liquid coolant. Further, high pressure exhaust blowdown pulses may be separated and thus engine performance may be improved. Thus, a temperature of the exhaust gases and cylinder head components may be reduced. Furthermore, cooling of the exhaust gases may reduce thermal degradation of downstream components, such as a turbocharger and/or an emission control system. Further still, the temperature sensor may send a temperature signal to a controller of the vehicle, such that the controller may send an early over-temperature condition signal to an operator of the vehicle. Upon receiving the early over-temperature signal, the operator may stop the vehicle before thermal degradation occurs. Thus, performance and life of the engine, turbocharger, and emission control system can be improved when the cylinder head described above is utilized.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.